package com.tanhua.server.interceptor;

import com.fasterxml.jackson.databind.ObjectMapper;
import com.tanhua.server.utils.Cache;
import org.apache.commons.codec.digest.DigestUtils;
import org.apache.commons.lang3.StringUtils;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.beans.factory.annotation.Value;
import org.springframework.data.redis.core.RedisTemplate;
import org.springframework.stereotype.Component;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.method.HandlerMethod;
import org.springframework.web.servlet.HandlerInterceptor;

import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

/**
 * @Description AUTO
 * @ClassName RedisCacheInterceptor
 * @Author ZhengXinjie
 * @date 2021.02.21 08:31
 */
@Component
public class RedisCacheInterceptor implements HandlerInterceptor {

    @Value("{tanhua.cache.enable}")
    private boolean enable;

    @Autowired
    private RedisTemplate<String, String> redisTemplate;

    private static final ObjectMapper MAPPER = new ObjectMapper();

    @Override
    public boolean preHandle(HttpServletRequest request, HttpServletResponse response, Object handler) throws Exception {
        // 缓存的全局开关校验
        if(!enable){
            return true;
        }

        // 校验handler是否是HandlerMethod
        if(!(handler instanceof HandlerMethod)){
            return true;
        }

        // 判断是否为get请求
        if(!((HandlerMethod) handler).hasMethodAnnotation(GetMapping.class)){
            return true;
        }

        // 判断是否添加了@Cache注解
        if(!((HandlerMethod) handler).hasMethodAnnotation(Cache.class)){
            return true;
        }

        //缓存命中
        String redisKey = createRedisKey(request);
        // 查找redis中的redisKey
        String cacheData = this.redisTemplate.opsForValue().get(redisKey);
        if(StringUtils.isEmpty(cacheData)){
            //缓存未命中
            return true;
        }

        // 将data数据进行响应
        response.setCharacterEncoding("UTF-8");
        response.setContentType("application/json; charset=utf-8");
        response.getWriter().write(cacheData);

        return false;

    }

    /**
     * 生成redis中的key，规则：SERVER_CACHE_DATA_MD5(url + param + token)
     * @param request 请求
     * @return redisKey
     */
    public static String createRedisKey(HttpServletRequest request) throws Exception {
        String url = request.getRequestURI();
        // 传递的参数封装成json对象
        String param = MAPPER.writeValueAsString(request.getParameterMap());
        // 获取请求头携带的token
        String token = request.getHeader("Authorization");

        String data = url + "_" + param + "_" + token;
        return "SERVER_CACHE_DATA_" + DigestUtils.md5Hex(data);
    }
}

